use iconfiguration

Controller/HanyadikHetVanService.cs

@@ -21,7 +21,7 @@ namespace hanyadikhetvan
 
         public HanyadikHetVanDTO HanyadikHetVan()
         {
-            return new HanyadikHetVanDTO();
+            return new HanyadikHetVanDTO(_configuration["HanyadikHetVan:StartDate"]);
         }
     }
 }

DTO/HanyadikHetVanDTO.cs

@@ -7,6 +7,13 @@ namespace hanyadikhetvan.DTO
 {
     public class HanyadikHetVanDTO
     {
-        public int HanyadikHet => (DateTime.Now - (DateTime.Parse(Environment.GetEnvironmentVariable("HANYADIKHET_STARTDATE")))).Days / 7;
+        private readonly DateTime startdate;
+
+        public HanyadikHetVanDTO(string startdate)
+        {
+            this.startdate = DateTime.Parse(startdate);
+        }
+
+        public int HanyadikHet => (DateTime.Now - startdate).Days / 7;
     }
 }

Properties/launchSettings.json

@@ -23,6 +23,7 @@
       "launchUrl": "swagger",
       "environmentVariables": {
         "HANYADIKHET_STARTDATE": "2021-02-08",
+        "HanyadikHetVan__StartDate": "2021-02-08",
         "ASPNETCORE_ENVIRONMENT": "Development"
       },
       "dotnetRunMessages": "true",

Startup.cs

@@ -26,6 +26,7 @@ namespace hanyadikhetvan
         // This method gets called by the runtime. Use this method to add services to the container.
         public void ConfigureServices(IServiceCollection services)
         {
+// services.Configure<HanyadikHetVanService>(Configuration.GetSection("HanyadikHetVan"));
             services.AddTransient<HanyadikHetVanService>();
             services.AddControllers();
         }

appsettings.json

@@ -1,4 +1,7 @@
 {
+  "HanyadikHetVan": {
+    "StartDate": "2021-02-01"
+  },
   "Logging": {
     "LogLevel": {
       "Default": "Information",